Active food packaging is a critically important area that provides the foundation for keeping packaged food fresh while reducing microbe load, inhibiting microbe growth and/or keeping the product substantially microbe-free so that the nutritional value of the food can be maintained and loss from spoilage minimized. Consequently, because of advances in food packaging technology, more people have access to fresh food. Food producers, packers and sellers can also provide a higher quality product while sustaining less economic loss due to product spoilage.
Active packaging, i.e., packaging that incorporates methods and/or compositions for the inhibition of microbial growth, covers many areas, but can be broadly defined in the art as the use of chemical or biochemical systems, including the use of antimicrobial and/or antifungal agents, that preserve the freshness and extend the shelf life of a food product by interacting with the food or the atmosphere surrounding the food either constantly or via controlled release. One prior art method of controlling the package atmosphere is the use of what is termed in the food packaging industry as Modified Atmosphere Packaging (MAP) where, generally, the relative concentrations of oxygen, carbon dioxide and nitrogen are adjusted relative to each other to preserve the integrity and freshness of the particular packaged item. A good review of Modified Atmosphere Packaging is provided in the art by Church and Parsons (Church, I. J. & Parsons, A. L.: (1995) Modified Atmosphere Packaging Technology: A Review, Journal Science Food Agriculture, 67, 143-152), as well as Beaudry (Beaudry, R., MAP as a Basis for Active Packaging, in Intelligent and Active Packaging for Fruits and Vegetables, C. L. Wilson, Ed. CRC Press, 2007. pp. 31-55).
The term “antimicrobial” with respect to food packaging is known in the art to include any composition and/or method to reduce or inhibit microbial growth (including bacteria and fungi) and, therefore, has wide breadth in the art. For example, as explained in López-Rubio (López-Rubio, A., et. al., (2004). Overview of Active Polymer-Based Packing Technologies for Food Applications. Food Rev. Int., 20(4): 357-87, p. 366), carbon dioxide often exerts a microbiological inhibitory effect in meats, cheeses and baked goods, but excess carbon dioxide may also adversely affect the taste or texture of the food product as well. Still, use of carbon dioxide is considered by those of skill in the art to be an antimicrobial agent. To the extent that there are gases like carbon dioxide, and others as detailed below, that provide an antimicrobial effect, we classify their use together in food packaging as a type of antimicrobial packaging. Exemplary representation of the current state of the food packaging art is provided below.
1. Description of Related Art—Food Packaging Pads
In food packaging, an absorbent pad can be used for a variety of reasons, but is typically used to protect food articles from damage and to absorb moisture or biofluids that would otherwise compromise the freshness, integrity and appearance of the packaged food. Typically, a superabsorbent polymer, or SAP, is employed in granular or fiber form along with a nonwoven pad comprised of spunbond or meltblown synthetic fibers or paper pulp fibers, to absorb fluid. The pad typically can employ a film-based top and bottom layer with perforations that allow the fluid to reach the nonwoven absorbent layer but protect the food product from stray fibers.
U.S. Pat. No. 6,270,873, assigned to Sealed Air Corporation, teaches a food pad that comprises a top sheet and a bottom sheet with an absorbent nonwoven layer in between. According to the disclosure, the absorbent layer can be situated in the construction in a variety of ways. The top layer and bottom layer are sealed to confine the absorbent layer and microperforations are used in the various layers to allow fluid to permeate the sheet layers and reach the absorbent. However, such multilayer construction can be expensive and microperforations may become plugged by particulates. The patent does not have any teaching on biodegradable thermoplastic polymers and nor on the actual specific manufacturing process with regard to the involvement of antimicrobial and antifungal agents.
U.S. Pat. No. 7,732,036, assigned to Paper-Pak Industries, describes a shaped absorbent pad system whereby the pad system is sealed ultrasonically such that it prevents the pad from bursting due to fluid absorption, specifically with the usage of side panels and hinge connects. It also provides for multiple layers and also, among other features, allows that no perforations be used for fluid to flow into the absorbent pad. It also provides examples of using active agents to preserve packaged food freshness. However, this pad design is also relatively costly to manufacture and the envisioned active ingredients may not be optimal for longer term food preservation. Further, the pad design is not biodegradable and does not provide controlled release of an antimicrobial agent. And, finally, the pad system does not utilize biodegradable thermoplastic non-woven fibers that are specifically oriented and constructed to allow fluid absorption in manner that allows the adequate expansion of the pad.
U.S. Pat. No. 5,444,113, assigned to Ecopol, LLC, discloses products made of degradable materials that include a hydrolytically degradable polymer. Poly(lactic) acid is specifically mentioned, which is also called polylactide, which the authors further cite as a polydioxanedione. The authors list numerous forms of the biodegradable polymers such as laminates, foams, powders and adhesives, and they list ways to modify the polymers to enhance biodegradability. They specifically state that the materials in their invention degrade in a time period of a few months to a few years. However, they do not teach how antimicrobials may be incorporated into the degradable polymers of their disclosure nor how controlled release of the antimicrobial agent may be achieved. Further, they do not disclose how specific meltblown non-woven layer materials with enhanced mechanical and performance properties can be constructed and manufactured.
2. Description of Related Art—Antimicrobial, Biocidal, Antifungal Food Packaging Aspects
U.S. Pat. No. 7,585,530, assigned to Paper-Pak Industries, discloses a multiphase food pad absorbent system that absorbs fluids and inhibits bacterial growth by incorporating bacteriostatic and/or bactericidal ingredients and, optionally, the ability to modify the atmosphere inside the package, with other options that include reaction promoters in the food pad to maintain the integrity and safety of the packaged article. It is also important to note that in U.S. Pat. No. 7,585,530, no mention of biodegradability is made. U.S. Pat. No. 7,585,530 focuses on absorbency and the use of superabsorbent materials specifically in related to meat products within the context of using an organic acid bacterial inhibitor. U.S. Pat. No. 7,585,530 also discloses atmosphere modification within the package by CO2/O2 modification, and discloses the use of enzymes to modify the atmosphere, specifically to reduce the oxygen content. Although this prior art claims antimicrobial materials in an absorbent medium, along with methods to modify the atmosphere inside the package, the art does not teach methods of controlled release of the antimicrobial agent(s) that would prolong the shelf life of the packaged food products.
U.S. Pat. No. 7,799,361, assigned to Paper-Pak Industries, similarly to U.S. Pat. No. 7,585,530, demonstrates an absorbent food pad constructed from tissue layers and is specifically related to absorbing liquid purge emanating from meat and poultry produce and using bacterial inhibitors to inhibit the growth of bacteria in the liquid purge itself. Also disclosed is a carbon dioxide generating system. There is no mention of the usage of antimicrobial agents in a controlled release manner and no discussion of a food pad that is biodegradable and no teaching of all aspects of the food pad non-woven construction including the calendaring of a non-woven biodegradable thermoplastic polymer.